#------------------------------------------------------------------------------
# Copyright (c) 2013, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
#------------------------------------------------------------------------------
from atom.api import Bool, Typed, ForwardTyped, set_default
from enaml.core.declarative import d_, observe
from enaml.image import Image
from .control import Control, ProxyControl
class ProxyImageView(ProxyControl):
""" The abstract definition of a proxy ImageView object.
"""
#: A reference to the ImageView declaration.
declaration = ForwardTyped(lambda: ImageView)
def set_image(self, image):
raise NotImplementedError
def set_scale_to_fit(self, scale):
raise NotImplementedError
def set_allow_upscaling(self, allow):
raise NotImplementedError
def set_preserve_aspect_ratio(self, preserve):
raise NotImplementedError
def get_aspect_ratio(self):
raise NotImplementedError
[docs]
class ImageView(Control):
""" A widget which can display an Image with optional scaling.
"""
#: The image to display in the viewer.
image = d_(Typed(Image))
#: Whether or not to scale the image with the size of the component.
scale_to_fit = d_(Bool(False))
#: Whether to allow upscaling of an image if scale_to_fit is True.
allow_upscaling = d_(Bool(True))
#: Whether or not to preserve the aspect ratio if scaling the image.
preserve_aspect_ratio = d_(Bool(True))
#: An image view hugs its width weakly by default.
hug_width = set_default('weak')
#: An image view hugs its height weakly by default.
hug_height = set_default('weak')
#: A reference to the ProxyImageView object.
proxy = Typed(ProxyImageView)
[docs]
def layout_constraints(self):
"""Add constraints to preserve the aspect ratio.
"""
if self.proxy_is_active and self.preserve_aspect_ratio:
ratio = self.proxy.get_aspect_ratio()
return self.constraints + [self.width == ratio*self.height]
return self.constraints
#--------------------------------------------------------------------------
# Observers
#--------------------------------------------------------------------------
@observe('image', 'scale_to_fit', 'allow_upscaling', 'preserve_aspect_ratio')
def _update_proxy(self, change):
""" An observer which sends state change to the proxy.
"""
# The superclass handler implementation is sufficient.
super(ImageView, self)._update_proxy(change)